A new technique of closed chest left atrial cannulation has been described and published. Using this technique, a specially designed heparin coated cannula will be inserted into the left atrium. This same cannula will then be threaded through a roller pump and the other end of the cannula inserted into the femoral artery. Using a single contiguous heparin coated tube, left atrial-femoral bypass will be instituted. Initially, short term studies for 24-36 will be carried out in acute experiments to determine if thromboembolization can be avoided by the heparin bond approach. The heparin will be bonded to the surface of the polyvinylchloride cannula by using a tridodecylmethylammoniumchloride (TDMAC)-heparin bond. After successful short term studies, prolonged left heart bypass of 36-84 hours will be evaluated using a chronic animal with the closed cleft transseptal cannulation approach. Flow rates during prolonged left heart bypass will remain in the range of 500-2000ml/min and blood will be drawn for determination of alteration in hematologic and clotting factors. Hemodynamic measurements will be carried out during the bypass to determine the percentage of cardiac output shunted away from the left ventricle. Following removal of the left atrial cannula, long term survival will be attempted.